Ditto all of the above..... raw nerves, adrenal exhaustion, all that goo that comes from living in an extended flight or fight mode..... it did me in & I felt similar to what you are describing.
Has your RAH relapsed during previous trips? Perhaps those memories are also triggering you emotionally even if you feel differently about it all now vs. before. (i.e. stronger in your recovery now, less concerned about his decisions, etc.) Even after I wasn't concerned about RAH relapsing during my work business trips, it still made me super anxious to go to my conferences for that next year or so. Just packing for the trip was enough to start that stressed out feeling churning in my system.